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Diamond Cuts

Diamond Cut Basics

What is diamond cut?

Cut refers to the proportions and relative angles of a faceted diamond. A diamond's cut should not be confused with its shape. Cut is a quality factor that determines value along with the other 4Cs of Carat Weight, Diamond Clarity, and Diamond Color.

How important is diamond cut?

Out of the 4Cs, diamond cut has the biggest impact on sparkle, brilliance and fire. A diamond's cut quality is a fine balance of proportions and angles, and most diamonds in the marketplace are average cuts. A well-cut diamond will sparkle more and will be livelier than a diamond that is poorly cut. When you are evaluating the 4Cs, understand that Cut trumps the others by turning a pebble of a diamond into a sparkling gem.

Diamond Anatomy and Proportions

To understand diamond cut, the first step is learning the parts of a diamond. Please visit: Anatomy of a Round Brilliant Diamond for the basic facet structure. The image below shows essential proportions of diamond cut.

Proportions and Light Return

The Ideal-Scope reference chart below illustrates the effect of proportions on light return. Well-cut stones show maximum brilliance while shallow or deep stones have zones where light escapes and is not returned to the viewer's eye. To learn more about using this diamond tool, please visit: Ideal-Scope Guide

How is diamond cut graded?

Three Approaches to Cut Grading:

1.

Proportions are measured with a Sarin,
Ogi, or Helium scanner.
Old systems use the worst proportion as the 'grade maker'. AGS used this flawed method until May 2005.

You can reject bad proportioned diamonds with Pricescope's free HCA for round diamonds and
AGA for other shapes.
These tools can narrow your search, but are not for final selection. Symmetry and other factors also need to be considered.

Direct assessment – Ideal-Scope viewers and photos show leakage
and light return. Hearts and Arrows viewers are for grading symmetry,
but some H&A's do not score <2 on HCA. Optical symmetry does not always equal the best light return.

The Brilliancescope and ISee-2 shine light
onto a diamond and give digital pixel counts. Both give a good indication of diamond performance, but neither gives the same grade for the same diamond.